全文获取类型
收费全文 | 71774篇 |
免费 | 10514篇 |
国内免费 | 2833篇 |
专业分类
化学 | 66351篇 |
晶体学 | 620篇 |
力学 | 1166篇 |
综合类 | 10篇 |
数学 | 7315篇 |
物理学 | 9659篇 |
出版年
2023年 | 284篇 |
2022年 | 317篇 |
2021年 | 801篇 |
2020年 | 1844篇 |
2019年 | 3152篇 |
2018年 | 1730篇 |
2017年 | 1363篇 |
2016年 | 4564篇 |
2015年 | 4406篇 |
2014年 | 4395篇 |
2013年 | 6428篇 |
2012年 | 5598篇 |
2011年 | 5130篇 |
2010年 | 4430篇 |
2009年 | 4454篇 |
2008年 | 4640篇 |
2007年 | 3987篇 |
2006年 | 3406篇 |
2005年 | 3478篇 |
2004年 | 3379篇 |
2003年 | 2720篇 |
2002年 | 3282篇 |
2001年 | 2179篇 |
2000年 | 1948篇 |
1999年 | 894篇 |
1998年 | 492篇 |
1997年 | 391篇 |
1996年 | 452篇 |
1995年 | 334篇 |
1994年 | 292篇 |
1993年 | 347篇 |
1992年 | 296篇 |
1991年 | 205篇 |
1990年 | 197篇 |
1989年 | 168篇 |
1988年 | 163篇 |
1987年 | 152篇 |
1986年 | 151篇 |
1985年 | 242篇 |
1984年 | 214篇 |
1983年 | 163篇 |
1982年 | 144篇 |
1981年 | 147篇 |
1980年 | 117篇 |
1979年 | 120篇 |
1978年 | 101篇 |
1977年 | 99篇 |
1976年 | 95篇 |
1975年 | 91篇 |
1973年 | 97篇 |
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
81.
G. Montero L. Gonzlez E. Flrez M. D. García A. Surez 《Numerical Linear Algebra with Applications》2002,9(3):239-247
Parallel preconditioners are presented for the solution of general linear systems of equations. The computation of these preconditioners is achieved by orthogonal projections related to the Frobenius inner product. So, minM∈??∥AM?I∥ F and matrix M0∈?? corresponding to this minimum (?? being any vectorial subspace of ??n(?)) are explicitly computed using accumulative formulae in order to reduce computational cost when subspace ?? is extended to another one containing it. Every step, the computation is carried out taking advantage of the previous one, what considerably reduces the amount of work. These general results are illustrated with the subspace of matrices M such that AM is symmetric. The main application is developed for the subspace of matrices with a given sparsity pattern which may be constructed iteratively by augmenting the set of non‐zero entries in each column. Finally, the effectiveness of the sparse preconditioners is illustrated with some numerical experiments. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
82.
83.
Marí a J. Martí n Dragan Vukotic 《Proceedings of the American Mathematical Society》2006,134(6):1701-1705
We show that every composition operator which is an isometry of the Dirichlet space is induced by a univalent full map of the disk into itself that fixes the origin. This is an analogue of the Hardy space result for inner functions due to Nordgren. The proof relies on the Stone-Weierstrass theorem and the Riesz representation theorem.
84.
85.
5‐Amino‐4‐methyl‐2‐phenyl‐6‐substitutedfuro[2,3‐d]pyrimidines ( 2a‐c ) were reacted with 2,5‐dimethoxytetrahydrfuran to afford the pyrrolyl derivatives 3a‐c . Compound 3a was chosen as intermediate for the synthesis of poly fused heterocycles incorporated furopyrimidines moiety 4–11 . Some of the synthesized compounds were screened for their antibacterial and antifungal activities. 相似文献
86.
(S)-2-[2-(p-Tolylsulfinyl)phenyl]acetaldehyde reacts with different O-silylated ketenethioacetals in the presence of Yb(OTf)3 yielding β-hydroxythioesters in high yields and diastereoselectivities. The obtained compounds were readily transformed into β-hydroxyacids and their corresponding diols. These Mukaiyama aldol reactions are a direct evidence of the ability of the sulfinyl group to control 1,5- and 1,6-asymmetric induction processes. 相似文献
87.
Lubomír Kubáček 《Applications of Mathematics》2006,51(6):565-582
Some remarks to problems of point and interval estimation, testing and problems of outliers are presented in the case of multivariate
regression model.
This work was supported by the Council of Czech Government J14/98:153100011. 相似文献
88.
We analyze the dynamics of an AdS5 braneworld with matter fields when gravity is allowed to deviate from the Einstein form on the brane. We consider exact five-dimensional warped solutions which are associated with conformal bulk fields of weight –4 and describe on the brane the following three dynamics: those of inhomogeneous dust, of generalized dark radiation, and of homogeneous polytropic dark energy. We show that, with modified gravity on the brane, the existence of such dynamical geometries requires the presence of non-conformal matter fields confined to the brane. 相似文献
89.
90.
Ricardo Celorrio Vı́ctor Domínguez Francisco-Javier Sayas 《Comptes Rendus Mathematique》2002,334(10):923-926
In this work we study the solution of Laplace's equation in a domain with holes by an iteration consisting of splitting the problem in an exterior one, around the holes, plus an interior problem in the unholed domain. We show the existence of a decomposition of the solution when the exterior problem is represented by means of a single-layer protential. Also, for the three-dimensional case and with some adjustments for the two-dimensional case, we prove convergence of the method by writing the iteration as a Jacobi iteration for an operator equation and studying the spectrum of the iteration operator. To cite this article: R. Celorrio et al., C. R. Acad. Sci. Paris, Ser. I 334 (2002) 923–926. 相似文献